1. To fill the fuel tank of a vehicle (with a particular type of fuel). We'll need to tank up before we get on the highway tomorrow. I'm going to tank up on gas at the next rest stop.

2. To eat or drink (something) until one is full. We're going to be having dinner soon, so don't tank up on chips and candy. We stopped halfway to tank up on trail mix and water.

3. To drink alcohol to the point of intoxication. Don't tank up during lunch—we don't want any mistakes during the meeting this afternoon. He just sat silently at the bar, tanking up on whiskey and soda.

4. To ply someone with alcohol to the point of intoxication. In this usage, a noun or pronoun can be used between "tank" and "up." It was my 21st birthday, so my friends tanked me up on all manner of liquor. Someone spiked the punch to try to tank up the entire auditorium of students.

5. Of a substance, to cause someone to become intoxicated due to having been ingested. In this usage, a noun or pronoun is used between "tank" and "up." Wow, that cocktail you made me really tanked me up!